1. Field of the Invention
This invention relates to a color toner, and more particularly to a cyan color toner for developing electrostatic images.
2. Description of the Prior Art
Electrostatic printing or electrophotography has been well-known as a process for developing an electrostatic latent image with a toner to form a visible image. For example, the processes described in the specifications of U.S. Pat. Nos. 2,297,691, 3,666,363 and 4,071,361 have been known as electrophotography. Some of these processes include forming electrostatic latent images on an electrophotographic photosensitive member by various means using photoconductive substance and then developing the latent image with a toner. An alternative process includes transferring powder images onto paper or the like, if necessary, and fixing it by heating, pressing or using solvent vapor to yield visible images. In order to obtain a multicolor image, the original is exposed to light through a color separating filter and the above-mentioned process is repeated at least twice using color toners such as yellow, magenta and cyan toners, and the toner images are superposed to produce a color image.
Such color toners are required indispensably to have excellent spectral reflection characteristics, while hue is very important criterion of selecting a colorant for the toner.
As colorants used for cyan toners, there have been used copper phthalocyanine represented by C. I. Pigment blue 15 and its sulfonamide derivatives disclosed in the specifications of British Patent Publication No. 1,307,544, Japanese Patent Publication No. Sho. 54-3372 and so on. These colorants, however, assume blue with strong reddish tint, and therefore they are not suitable for use without combining other kind of colorant in view of its hue.
This invention has been made under such a circumstance.